1. Field of the Invention
The present invention relates to a method of converting a carboxylic acid or a carboxylic acid derivative into the corresponding alcohol.
2. Description of the Related Art
Hitherto, various studies have been conducted on methods of preparing an alcohol from a carboxylic acid or a carboxylic acid ester by use of hydrogen.
A method of preparing a corresponding alcohol from a carboxylic acid is known in which the carboxylic acid is reduced by hydrogen using a rhenium catalyst system (Jpn. Pat. Appln. KOKAI Publication No. 57-32237). However, the method using the rhenium catalyst system is not a general one since it requires high pressure in the range of 50 to 500 arm, and a special apparatus, which involves a high cost.
Among the catalyst which can be used in a method of preparing an alcohol from a carboxylic acid ester, there are, besides the rhenium catalyst, copper-metal oxide catalyst systems, such as copper chromite, copper-zinc oxide, copper-molybdenum oxide, copper ferric oxide, and copper-zirconium oxide (Jpn. Pat. Appln. KOKAI Publication Nos. 63-141937, 2-36135, 3-220143, 54-32191, 52-156192 or 3-128334). Catalysts other than the copper catalyst systems have been proposed. Examples are a nickel catalyst which incorporates tin, germanium, or lead (EP-A-172091), a rhodium catalyst which incorporates tin, germanium, or lead (EP-A-95408 or Jpn. Pat. Appln. KOKAI Publication No. 58-216131), a catalyst consisting of rhenium and a group VIII noble metal (DE-A-3217429), and the like. Catalysts which contain palladium and zinc oxide, or rhenium and zinc oxide on a carrier have also been proposed (Jpn. Pat. Appln. KOKAI Publication No. 2-36136). Using the above-mentioned catalysts, the corresponding alcohol can be obtained from a carboxylic acid ester by reduction with hydrogen gas.
Also known are a method in which a carboxylic acid or a carboxylic acid ester is reduced by using an alcohol as a hydrogen source to produce an alcohol (Jpn. Pat. Appln. KOKAI Publication No. 64-15136), and a method in which an aldehyde or a ketone is reduced to produce an alcohol in the presence of a homogeneous catalyst (Jpn. Pat. Appln. KOKAI Publication Nos. 61-204143 and 62-252737).
Further known is a reduction method by electrolysis (Jpn. Pat. Appln. KOKAI Publication No. 58-117887). This method can be applied only to preparing para-substituted benzyl alcohol. The alcohols corresponding to other carboxylic acids cannot be obtained in this method.
As described above there are various methods of preparing alcohol by reduction. The reduction method using a hydrogen gas, in particular, needs to be performed under relatively high temperature and high pressure. This condition involves high-cost equipment and is dangerous due to inflammable hydrogen gas. The cost and safety problems can be avoided in a reduction method using an alcohol as a hydrogen source, but a restricted source of usable carboxylic acid is another problem. For instance, the alcohol corresponding to a long chain carboxylic acid cannot be obtained in an acceptable yield in this method.